OATITIE8 IF THE ROCK. 2G3 



existence of subterraneous cavities in the yellalas or rapids 

 of the river Congo was discovered. The pongo of Manse- 

 riche, which ought rather to be called a strait than a fall, 

 ingulfs, in a manner not yet sufficiently explored, a part of 

 the waters and all the floating wood of the Upper Maranon. 



The spectator, seated on the bank of the Orinoco, with 

 his eyes fixed on those rocky dikes, is naturally led to 

 inquire whether, in the lapse of ages, the falls change their 

 form or height. I am not much inclined to believe in such 

 effects of the shock of water against blocks of granite, and 

 in the erosion of siliceous matter. The holes narrowed 

 toward the bottom, the funnels that are discovered in the 

 raudales, as well as near so many other cascades in Europe, 

 are owing only to the friction of the sand, and the move- 

 ment of quartz pebbles. We saw many such, whirled per- 

 petually by the current at the bottom of the funnels, and 

 contributing to enlarge them in every direction. The 

 pongos of the river Amazon are easily destroyed, because 

 the rocky dikes are not granite, but a conglomerate, or red 

 sandstone with large fragments. A part of the pongo of 

 Rentema was broken down eighty years ago, and the course 

 of the waters being interrupted by a new bar, the bed of 

 the river remained dry for some hours, to the great astonish- 

 ment of the inhabitants of the village of Payaya, seven 

 leagues below the pongo. The Indians of Atures assert 

 (and in this their testimony is contrary to the opinion of 

 Caulin) that the rocks of the raudal preserve the same 

 aspect ; but that the partial torrents into which the great 

 river divides itself as it passes through the heaped blocks 

 of granite, change their direction, and carry sometimes 

 more, sometimes less water towards one or the other bank ; 

 but the causes of these changes may be very remote from 

 the cataracts, for in the rivers that spread life over the 

 surface of the globe, as in the arteries by which it is 

 diffused through organized bodies, all the movements are 

 propagated to great distances. Oscillations, that at first 

 seem partial, react on the whole liquid mass contained in 

 the trunk as well as in its numerous ramifications. 



Some of the Missionaries in their writings have alleged 

 that the inhabitants of Atures and Maypures have been 

 truck with deafiiess by the noise of the* Great Cataract* 



